Hello,
I am looking for something where I can add my dates and schedules/tasks on my computer and view them on my blackberry.

I only want to have to add events once and not have to worry about entering them twice. Many of the time, I will add something for a few months ahead and I check my computer and blackberry the same.

I don't know how this would work, but something that uses a single mySQL database could be handy, but this would mean that it requires either a constant connection, or can update regularly.

I have tried looking in lots of places, but all I can find is products which will work through bring syncronised through connecting your PDA to your computer. Such as with a IPAQ and using MS Active Sync to update your calandar.

Well you can fully synch the BB with Outlook calendar and tasks using the DeskTop Manager.... If you need something realtime you will need to use BES and that can be hosted by your company or a third party.